The overall purpose of this award application is to support the patient-oriented research program and career development of a beginning clinical investigator in hospital-acquired infections in the elderly. Long-term objective: Elderly (> 65 years old) adults are particularly vulnerable to nosocomial infections. Despite significant morbidity associated with surgical site infection (SSI) and infections caused by multi-drug resistant bacteria (MDRB), investigators have paid relatively little attention to these infections in elderly hospitalized patients. The broad objectives for this application are to identify risk factors and interventions to improve outcomes of elderly hospitalized persons. Specific aims: 1) Create risk models for the development of SSI and MDRB in the elderly and to test a prior hypotheses regarding particular risk factors; and 2) quantify the impact of SI and nosocomial MDRB on health outcomes in the elderly. Health outcomes (mortality, duration of hospitalization and hospital costs) will be assessed for the 90-day period following surgery (for SSI) and infection (for MDRB). In addition, the impact of SSI on ADL disability will also be assessed. Methods: The project will utilize 10 study hospitals and an infection control infrastructure that includes 3 physician epidemiologists and over 20 infection control practitioners. Patients with SSI and nosocomial infection and colonization due to MDRB are currently identified through prospective surveillance and have been and will continued to be prospectively entered into electronic databases at study hospitals. Additional study data will be obtained from patient charts and hospital databases. For the study of SSI, elderly patients with SSI will be studied as cases and will be compared to elderly operative patients without SSI. ADL disability will be assessed preoperatively through chart review and postoperatively by phone interview 90 days after surgery. For the study of MDRB, elderly patients with an initial episode of nosocomial MDRB will be studied as cases and will be compared to elderly patients without infection or colonization due to MDRB. For the risk model analysis, patients colonized or infected with MDRB will be included as cases; and for the health outcomes analysis, only patients with infections due to MDRB will be studied as cases. The risk factor identified for SSI and MDRB and the impact of SSI and MDRB on health outcomes will be used to design and implement future preventive interventions.